This invention pertains to the art of exothermic cutting torches or cutting bars and more particularly to consumable cutting torches or cutting rods.
The invention is more particularly applicable to an oxygen-fed cutting torch used for cutting, boring, burning, and the like of hard base materials. However, it will be appreciated that the invention has broader applications and may be advantageously employed in other environments and applications.
Conventional cutting torches or thermic lances are well known in the art as represented by U.S. Pat. Nos. 4,114,863; 4,416,444; and 3,921,542. Each of these patents generally teaches the use of a first or outer tube through which is fed an oxidizing gas such as oxygen. The oxidizing gas is ignited in any known manner. For example, an electric arc may be used to initiate the combustion process.
The outer tube may receive a second or inner tube, and/or a set of consumable metallic rods. Gas passages are defined between the rods and tubes to convey the oxidizing gas from a gas supply connected at one end to a combustion end of the cutting torch. The volatile nature of the combustion is used to pierce hard base materials such as cast iron, steel, concrete, or rock. As the combustion process continues, the torch is consumed and, therefore, must be periodically replaced.
The length of time between replacement of cutting torches is a primary factor in considering the efficiency of a particular design. Another major factor is the effectiveness of the cutting operation. Still another factor is the expense of manufacture of the cutting torches. All of these factors, and others, must be considered in evaluating efficiency, performance, and effectiveness of operation.
Other performance characteristics are an important consideration when developing an improved cutting torch. For example, the structure in U.S. Pat. No. 4,114,863 has been effective in reducing the "splatter" associated with such a cutting operation. The tube within a tube design, having plural rods disposed in the inner tube, has proved to be highly successful in concentrating the thermic reaction. It is believed that the inner and outer tubes define a gas envelope that confines the splatter associated with the cutting operation.
As discussed in that patent, the tubes are locked against relative axial movement through use of plural detents that extend radially inward from the outer tube toward the outer periphery of the inner tube. Although deemed highly effective in retaining the tubes together, the cross sectional profile of the cutting torch is slightly altered and may have a tendency to disrupt the focussed action of the tube within a tube design.
Retention of the rods in the inner tube is also difficult. Either a friction fit can be used to maintain the rods in place or, alternatively, a detent arrangement similar to that employed between the inner and outer tubes can be used. Again, the cross sectional profile of the cutting torch can thereby change and have some minute impact on the consistency and uniformity of the cutting torch's performance.
Some recent attempts have been made to alter the manufacture of the cutting torches by roll forming a structure from a single strip or sheet of material. Although this is believed to be an inexpensive manner to manufacture a cutting torch, a potential problem exists with this arrangement. Specifically, the roll formed sheet is folded or crimped along a longitudinal seam. Oftentimes, the seam is filled with a plastic material to provide a gas tight seal. Any bending or flexing of the cutting torch may potentially expose the seam, particularly the plastic material, to stresses and strains that may breach the seal and result in undesirable leakage of the oxidizing gas.
The present invention contemplates new and improved apparatus and method of forming same that overcome the above referred to problems and others in an economical, simple manner.